Longitudinal optic phonon-plasmon coupling in delta-doped metamorphic InAlAs/InGaAs high-electron-mobility transistor structures on GaAs substrates

InAlAs/InGaAs metamorphic high-electron-mobility transistor structures with different spacer layers on GaAs substrates are characterized by Raman meas urements. The influence of In0.52Al0.48As spacer thickness on longitudinal optic phonon-plasmon coupling is investigated. It is found that the intensi ty of GaAs-like longitudinal optic phonon, which couples with collective in tersubband transitions of two-dimensional electron gas, is strongly affecte d by the different subband energy spacings, subband electron concentrations , and wave function distributions, which are determined by different spacer thicknesses. (C) 2001 American Institute of Physics.